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English: Depiction of the various key subsets of CD4-positive T cells with corresponding associated cytokines and transcription factors. Figure legend T cells leave the thymus in a naïve, antigen non-experiened state. After contact with antigen, T cells may take on one of numerous subsets.
The T helper cells (T h cells), also known as CD4 + cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines .
In molecular biology, CD4 (cluster of differentiation 4) is a glycoprotein that serves as a co-receptor for the T-cell receptor (TCR). CD4 is found on the surface of immune cells such as helper T cells , monocytes , macrophages , and dendritic cells .
T cells are grouped into a series of subsets based on their function. CD4 and CD8 T cells are selected in the thymus, but undergo further differentiation in the periphery to specialized cells which have different functions. T cell subsets were initially defined by function, but also have associated gene or protein expression patterns.
In lymphocyte populations, the co-receptor CD4 is found on helper T cells and the co-receptor CD8 is found on cytotoxic T cells. CD4 has four Ig domains in its extracellular portion and functions as a monomer. CD8, in contrast, functions as a dimer with either two identical alpha chains or, more typically, with an alpha and beta chain.
T-cell surface glycoprotein CD1e is a protein in humans encoded by the CD1E gene. CD2: a type I transmembrane protein found on thymocytes, T cells, and some natural killer cells that acts as a ligand for CD58 and CD59 and is involved in signal transduction and cell adhesion; expressed in T-cell acute lymphoblastic leukemia and T-cell lymphoma. CD3*
The threshold for positive and negative selection of developing T cells is regulated by the bound between the Lck and co-receptors. [10] There are two main pools of T cells which mediate adaptive immune responses: CD4+ T cells (or helper T cells), and CD8+ T-cells (or cytotoxic T cells) which are MHCII-and MHCI restricted respectively.
In immunology, a naive T cell (T h 0 cell) is a T cell that has differentiated in the thymus, and successfully undergone the positive and negative processes of central selection in the thymus. Among these are the naive forms of helper T cells ( CD4 + ) and cytotoxic T cells ( CD8 + ).